Dryer venting

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Joy, Jay made some good points. Judging from your
description, I'd guess that your feeling that
the duct has too much air resistance is probably
correct. The dryer manufacturer should give some
guidelines as to what length of duct is acceptable
(each bend is equivilent to several feet of straight
duct).
There may be some measures that can be taken
short of waming visitors while they wait for you to
answer the door however. I'd start by inspecting
the ducting. Is it solid or flex? Flex, even good
HVAC quality, has more air resistance than solid; if
it's "dryer duct" it's crap and should be replaced.
Where bends must be made, make them as gradual as
possible, two 45's would be better than a 90. Never
let the bend radius (as measured at the elbow's
centerline) be less than 1.5 the duct's diameter
(2x is even better).
The ducting should be sealed at each juction with
duct sealing mastic (not duct tape). If the ducting
is optimised but is still not performing adequately,
you can buy an in-line, pressure-activated booster
fan that should keep the air velocity up where the
lint won't settle out. Due the the nature of the
exhausted material (lint) I'd connect duct lengths
with pop-rivets rather than sheetmetal screws; screws
proved a place for the lint to catch. Good luck with it.